import Grad from './Grad'
const fade = Symbol('fade')
const lerp = Symbol('lerp')

export default class Perlin {
  perm = new Array(512)
  gradP = new Array(512)
  F2 = 0.5 * (Math.sqrt(3) - 1)
  G2 = (3 - Math.sqrt(3)) / 6
  F3 = 1 / 3
  G3 = 1 / 6
  grad3 = [
    new Grad(1, 1, 0),
    new Grad(-1, 1, 0),
    new Grad(1, -1, 0),
    new Grad(-1, -1, 0),
    new Grad(1, 0, 1),
    new Grad(-1, 0, 1),
    new Grad(1, 0, -1),
    new Grad(-1, 0, -1),
    new Grad(0, 1, 1),
    new Grad(0, -1, 1),
    new Grad(0, 1, -1),
    new Grad(0, -1, -1),
  ]
  p = [
    151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69,
    142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219,
    203, 117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175,
    74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230,
    220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76,
    132, 187, 208, 89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186,
    3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59,
    227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70,
    221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178,
    185, 112, 104, 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81,
    51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115,
    121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195,
    78, 66, 215, 61, 156, 180,
  ]

  constructor(seed = 0) {
    this.seed(seed)
  }

  seed(seed) {
    if (seed > 0 && seed < 1) {
      seed *= 65536
    }
    seed = Math.floor(seed)
    if (seed < 256) {
      seed |= seed << 8
    }
    for (let i = 0; i < 256; i++) {
      let v = 0
      if (i & 1) {
        v = this.p[i] ^ (seed & 255)
      } else {
        v = this.p[i] ^ ((seed >> 8) & 255)
      }
      this.perm[i] = this.perm[i + 256] = v
      this.gradP[i] = this.gradP[i + 256] = this.grad3[v % 12]
    }
  }

  simplex2(xin, yin) {
    let n0 = 0
    let n1 = 0
    let n2 = 0

    const s = (xin + yin) * this.F2
    let i = Math.floor(xin + s)
    let j = Math.floor(yin + s)
    const t = (i + j) * this.G2
    const x0 = xin - i + t
    const y0 = yin - j + t

    let i1 = 0
    let j1 = 1
    if (x0 > y0) {
      i1 = 1
      j1 = 0
    }

    const x1 = x0 - i1 + this.G2
    const y1 = y0 - j1 + this.G2
    const x2 = x0 - 1 + 2 * this.G2
    const y2 = y0 - 1 + 2 * this.G2

    i &= 255
    j &= 255

    const gi0 = this.gradP[i + this.perm[j]]
    const gi1 = this.gradP[i + i1 + this.perm[j + j1]]
    const gi2 = this.gradP[i + 1 + this.perm[j + 1]]

    let t0 = 0.5 - x0 * x0 - y0 * y0
    if (t0 < 0) {
      n0 = 0
    } else {
      t0 *= t0
      n0 = t0 * t0 * gi0.dot2(x0, y0)
    }
    let t1 = 0.5 - x1 * x1 - y1 * y1
    if (t1 < 0) {
      n1 = 0
    } else {
      t1 *= t1
      n1 = t1 * t1 * gi1.dot2(x1, y1)
    }
    let t2 = 0.5 - x2 * x2 - y2 * y2
    if (t2 < 0) {
      n2 = 0
    } else {
      t2 *= t2
      n2 = t2 * t2 * gi2.dot2(x2, y2)
    }
    return 70 * (n0 + n1 + n2)
  }

  simplex3(xin, yin, zin) {
    let n0 = 0
    let n1 = 0
    let n2 = 0
    let n3 = 0

    const s = (xin + yin + zin) * this.F3
    let i = Math.floor(xin + s)
    let j = Math.floor(yin + s)
    let k = Math.floor(zin + s)
    const t = (i + j + k) * this.G3
    const x0 = xin - i + t
    const y0 = yin - j + t
    const z0 = zin - k + t

    let [i1, j1, k1, i2, j2, k2] = [0, 1, 0, 1, 1, 0]
    if (x0 >= y0) {
      if (y0 >= z0) {
        i1 = 1
        j1 = 0
        k1 = 0
        i2 = 1
        j2 = 1
        k2 = 0
      } else if (x0 >= z0) {
        i1 = 1
        j1 = 0
        k1 = 0
        i2 = 1
        j2 = 0
        k2 = 1
      } else {
        i1 = 0
        j1 = 0
        k1 = 1
        i2 = 1
        j2 = 0
        k2 = 1
      }
    } else {
      if (y0 < z0) {
        i1 = 0
        j1 = 0
        k1 = 1
        i2 = 0
        j2 = 1
        k2 = 1
      } else if (x0 < z0) {
        i1 = 0
        j1 = 1
        k1 = 0
        i2 = 0
        j2 = 1
        k2 = 1
      } else {
        i1 = 0
        j1 = 1
        k1 = 0
        i2 = 1
        j2 = 1
        k2 = 0
      }
    }

    const x1 = x0 - i1 + this.G3
    const y1 = y0 - j1 + this.G3
    const z1 = z0 - k1 + this.G3
    const x2 = x0 - i2 + 2 * this.G3
    const y2 = y0 - j2 + 2 * this.G3
    const z2 = z0 - k2 + 2 * this.G3
    const x3 = x0 - 1 + 3 * this.G3
    const y3 = y0 - 1 + 3 * this.G3
    const z3 = z0 - 1 + 3 * this.G3

    i &= 255
    j &= 255
    k &= 255
    const gi0 = this.gradP[i + this.perm[j + this.perm[k]]]
    const gi1 = this.gradP[i + i1 + this.perm[j + j1 + this.perm[k + k1]]]
    const gi2 = this.gradP[i + i2 + this.perm[j + j2 + this.perm[k + k2]]]
    const gi3 = this.gradP[i + 1 + this.perm[j + 1 + this.perm[k + 1]]]

    let t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0
    if (t0 < 0) {
      n0 = 0
    } else {
      t0 *= t0
      n0 = t0 * t0 * gi0.dot3(x0, y0, z0)
    }
    let t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1
    if (t1 < 0) {
      n1 = 0
    } else {
      t1 *= t1
      n1 = t1 * t1 * gi1.dot3(x1, y1, z1)
    }
    let t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2
    if (t2 < 0) {
      n2 = 0
    } else {
      t2 *= t2
      n2 = t2 * t2 * gi2.dot3(x2, y2, z2)
    }
    let t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3
    if (t3 < 0) {
      n3 = 0
    } else {
      t3 *= t3
      n3 = t3 * t3 * gi3.dot3(x3, y3, z3)
    }

    return 32 * (n0 + n1 + n2 + n3)
  }

  perlin2(x, y) {
    let X = Math.floor(x)
    let Y = Math.floor(y)

    x = x - X
    y = y - Y

    X = X & 255
    Y = Y & 255

    const n00 = this.gradP[X + this.perm[Y]].dot2(x, y)
    const n01 = this.gradP[X + this.perm[Y + 1]].dot2(x, y - 1)
    const n10 = this.gradP[X + 1 + this.perm[Y]].dot2(x - 1, y)
    const n11 = this.gradP[X + 1 + this.perm[Y + 1]].dot2(x - 1, y - 1)

    const u = this[fade](x)

    return this[lerp](this[lerp](n00, n10, u), this[lerp](n01, n11, u), this[fade](y))
  }

  perlin3(x, y, z) {
    let X = Math.floor(x)
    let Y = Math.floor(y)
    let Z = Math.floor(z)

    x = x - X
    y = y - Y
    z = z - Z

    X = X & 255
    Y = Y & 255
    Z = Z & 255

    const n000 = this.gradP[X + this.perm[Y + this.perm[Z]]].dot3(x, y, z)
    const n001 = this.gradP[X + this.perm[Y + this.perm[Z + 1]]].dot3(x, y, z - 1)
    const n010 = this.gradP[X + this.perm[Y + 1 + this.perm[Z]]].dot3(x, y - 1, z)
    const n011 = this.gradP[X + this.perm[Y + 1 + this.perm[Z + 1]]].dot3(x, y - 1, z - 1)
    const n100 = this.gradP[X + 1 + this.perm[Y + this.perm[Z]]].dot3(x - 1, y, z)
    const n101 = this.gradP[X + 1 + this.perm[Y + this.perm[Z + 1]]].dot3(x - 1, y, z - 1)
    const n110 = this.gradP[X + 1 + this.perm[Y + 1 + this.perm[Z]]].dot3(x - 1, y - 1, z)
    const n111 = this.gradP[X + 1 + this.perm[Y + 1 + this.perm[Z + 1]]].dot3(x - 1, y - 1, z - 1)

    const u = this[fade](x)
    const v = this[fade](y)
    const w = this[fade](z)

    return this[lerp](
      this[lerp](this[lerp](n000, n100, u), this[lerp](n001, n101, u), w),
      this[lerp](this[lerp](n010, n110, u), this[lerp](n011, n111, u), w),
      v
    )
  }

  [fade](t) {
    return t * t * t * (t * (t * 6 - 15) + 10)
  }

  [lerp](a, b, t) {
    return (1 - t) * a + t * b
  }
}
